A solid phase synthesis method used for the chemical synthesis of a peptide, a nucleic acid and the like is a method where amino acids or nucleotide units are bound one by one with using a support for solid phase synthesis as the scaffold of reaction to thereby obtain a substance having an objective sequence.
Conventionally, a nonporous, high-swelling, low-crosslinked polystyrene particle has been generally used as the support for solid phase synthesis of a peptide (see, Non-Patent Document 1). On the other hand, in the case of solid phase synthesis of a nucleic acid, for example, since the diffusion rate of the synthesis reagent (e.g., nucleoside phosphoramidite) in such a support is slow to cause bad efficiency of the nucleic acid synthesis, a non-swelling porous glass particle (CPG; controlled pore glass) or silica gel having a large specific area has been heretofore used (see, Patent Document 1). In the case of using CPG or silica gel for the nucleic acid synthesis, an amino group is firstly introduced into the particle surface by using a silane coupling agent (e.g., aminopropyltriethoxysilane), and then nucleoside having a degradable linker for the cleavage of a nucleic acid is bound to the amino group. The nucleic acid synthesis is performed, for example, by a phosphoramidite method using this nucleoside linker-bound CPG as a starting material.
However, with recent development of nucleic acid pharmaceuticals, there is required a support for solid phase synthesis, that allows for synthesis of a larger amount of nucleic acid. Since the above-described non-swelling CPG has a limit in the specific surface area and is difficult to increase the synthesis rate, a crosslinked polystyrene particle which is porous and swellable has been developed according to the purpose (see, Patent Document 2). However, a support for solid phase synthesis, that enables synthesis of a nucleic acid with higher purity in a higher yield and realizes good cost performance, has been demanded.
Furthermore, also in using the crosslinked polystyrene particle for the nucleic acid synthesis, similarly to the CPG or silica gel, it is necessary to introduce a functional group such as amino group or hydroxyl group to a surface of the polystyrene particle in order for the binding between a nucleoside linker and the polystyrene particle. For example, there are a method including producing a copolymer particle by the copolymerization of styrene, divinylbenzene and chloromethylstyrene, and then treating the copolymer particle with ammonia to introduce an amino group, and a method including producing a copolymer particle by the copolymerization of styrene, divinylbenzene and acyloxystyrene, and then hydrolyzing the copolymer particle to introduce a hydroxyl group (see, Patent Documents 3 to 5). However, in either of these methods, the process is cumbersome.
Non-Patent Document 1: R. B. Merrifield, J. Am. Chem. Soc., 85, 2149, 1963
Patent Document 1: U.S. Pat. No. 4,458,066
Patent Document 2: U.S. Pat. No. 6,335,438
Patent Document 3 JP-A-58-210914
Patent Document 4: JP-A-52-023193
Patent Document 5: JP-A-5-086132